1. Field of the Invention
The present invention relates to an apparatus for processing images such as a digital still camera, a digital video camera, and the like. In addition, the invention further relates to an apparatus, a method, and a program that can be suitably used in such an image processing apparatus for the purpose of correcting the chromatic aberration of an image.
2. Description of the Related Art
Various kinds of electronic cameras are widely used nowadays. Some examples of such a variety of electronic cameras are: a digital still camera, a digital video camera, and a camera module that is mounted on or built in a variety of handheld electronic devices such as a mobile phone terminal and the like. These days, there is a demand for a small electronic camera that provides high magnification with a large number of pixels. In addition, there is also a need for high image quality.
However, it is getting more and more difficult to manufacture a lens that has a sufficiently high modulation transfer function (MTF) that can meet such an increasing demand for a smaller size, higher magnification, and a larger number of pixels. For example, as the size of a lens is reduced, the problem of “aberration” arises. Aberration is an undesirable difference in the focal positions of a formed image that is attributable to different wavelengths of light or screen positions. Besides the aberration problem, there arise a variety of image problems such as “shading” and “distortion”. Shading is an image problem of greater attenuation in the amount of incident light at the edge of a screen. Distortion is an image problem that arises depending on the position of an image on a screen.
One of such a variety of image problems that are attributable to a lens is aberration, or, more specifically, chromatic aberration. In connection therewith, a technique for correcting chromatic aberration through signal processing is described in Japanese Unexamined Patent Application Publication No. 2007-133591. According to the related-art chromatic aberration correction technique described in Japanese Unexamined Patent Application Publication No. 2007-133591, a judgment is made for each of pixels that make up an image as to whether a judgment-target pixel is a white overexposure pixel or not on the basis of the signal level of a luminance signal. Then, the result of judgment is stored as white overexposure information. A white overexposure map, which indicates the distribution of peripheral white overexposure pixels around a certain pixel of interest, is created on the basis of the stored white overexposure information. The created white overexposure map is stored for subsequent referential use. Then, according to the above-identified chromatic aberration correction technique of the related art, the integral value of the chromatic aberration amount of a certain pixel of interest as affected from its peripheral white overexposure pixels is calculated with the use of the white overexposure map that is stored as explained above and a pre-created chromatic aberration map, which indicates the distribution of chromatic aberration amount. Chromatic aberration correction is appropriately controlled by means of the calculated integral value of the chromatic aberration amount thereof.